"Royal hoax" station 2Day FM will submit its phone records to the UK inquest of Jacintha Saldanha to prove it sought permission to air the now-infamous prank call.

"We can confirm that four follow up calls were made to seek permission to air the call within an hour of the [prank call] being made," a 2Day FM spokesman told Fairfax Media. "Telstra has verified the calls as coming from our Sydney studio and all being received at the same number in London [at the King Edward VII's Hospital where Saldanha worked].

We were advised internally we didn't need permission because [Saldanha] was not a resident of Australia

"Because the calls were placed overseas, there was some debate about whether permission was needed. After the fourth call, we were advised internally we didn't need permission because [Saldanha] was not a resident of Australia."

British newspaper The Sunday Times has reported it is "highly likely" the four follow-up calls were taken by Saldanha herself. One call is believed to have ended abruptly but the others were long enough to allow conversations.

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Previously, the hospital claimed it received no follow-up phone calls from 2Day FM. It now accepts Saldanha may have taken the calls but not disclosed them before she committed suicide.

2Day FM's spokesman said the station's staff are unaware of who they spoke to when making the follow-up calls to the hospital. The calls were made by the production team rather than the hosts, Michael Christian and Mel Greig.

Jacintha Saldanha and her children.

In December of last year, the pair duped Saldanha into believing they were Prince Charles and the Queen. She transferred their call to another nurse, who divulged private information about the Duchess of Cambridge. Three days later, Saldanha killed herself.

The Sunday Times investigation into the tragedy portrays Saldanha as a deeply troubled woman.

The paper revealed that:

- In 1999, Saldanha's sisters Gladys and Mabel became suspects in a murder investigation after a woman – rumoured to be having an affair with Gladys's husband – was allegedly drugged, bound and thrown alive into a river; her corpse later washed up on a beach. The sisters have never been charged and the paper reports there is "an unproven suggestion that Jacintha helped post the bail". Jacintha and her husband, Benedict Barboza, later adopted Gladys' daughter, Lisha. The couple also has a biological son, Junal.

- Saldanha attempted suicide in late 2011 and may have again in early 2012. She was then diagnosed with a depressive disorder and referred to psychiatrists "in view of suicidal risk". Three days later, she was discharged with a warning note in her file: "There is a risk of deliberate self-harm and the need for 24-hour supervision." She was also advised to take medication.

- Saldanha was the night sister in charge of the hospital when she took the call – not simply a duty nurse or receptionist;

- The Duchess of Cambridge was being treated at the King Edward VII's Hospital last year for hyperemesis gravidarum, a severe vomiting condition potentially far more dangerous than morning sickness.

- After taking the prank call, Saldanha spoke to her husband once over the phone before killing herself – but never mentioned the hoax.

The Sunday Times reported that King Edward VII's hospital was not aware of these incidents or Saldanha's history of depression when it promoted her to night sister in charge.

Christian has since returned to work but Greig has taken action against her employer, accusing it of failing to provide a safe workplace. Fairfax Media understands that 2Day FM's parent company, Southern Cross Austereo, offered Greig several different jobs since the tragedy but she refused them all.

Greig has confirmed she will give evidence at the UK inquest, either in person or by video.

The inquest will begin on September 12.

For help or information visit beyondblue.org.au, call Suicide Helpline Victoria on 1300 651 251, or Lifeline on 131 114.